The present invention relates to a method of detecting a deflated tire on a vehicle suitable for cars, trucks, buses or the like.
Prior art methods of detecting a deflated or partially deflated tire on a vehicle operate by comparing the rolling radii of the tires. These systems utilize wheel speed signals such as those from electronic anti-lock braking systems (ABS) and compare the signals from each wheel in various ways to determine if one wheel is rotating significantly faster than the others thus indicating a reduced rolling radius caused by the tire being deflated.
The inventor of the present application however has found that for a deflated or partially deflated tire the rolling radius increases significantly with rotational speed due to increasing centrifugal forces which act on the tread mass on the radially outer periphery of the tire. While this phenomenon may also occur to a very limited degree with a normally inflated tire, it apparently is much greater in the case of a deflated tire in which the tread mass is unrestrained by tension on the casing plies.
As a result the speed signal differences, which the deflation warning system compares in order to detect the deflation, decrease with increasing vehicle speed. In fact at very high vehicle speed it has been found that a deflated tire can grow to a diameter beyond that of a normally inflated tire so that the deflation warning system would detect that the other normally inflated tires were apparently deflated.